The present invention relates to file systems, and more particularly, to techniques for improving the reliability of file systems.
A file system is a technique for storing and organizing computer files to facilitate the process of locating the files. File system software can be used to manage data blocks that are stored on a data storage device, such as a hard disk drive. The file system organizes the data blocks into files and directories. The file system also keeps track of which data blocks belong to which file and which data blocks are not being used. The data used by the file system to maintain such information is called metadata, and is often stored on the same storage device as the data files.
A hard disk drive may occasionally fail to provide accurate data to a user or application as a result of data block (sector) corruption. If such corruption occurs for file system metadata, an application may be unable to access data files and directories stored by the file system, even if these files and directories are not corrupted. Without a reliable backup of the data on a physically different storage device, or the implementation of a Redundant Array of Inexpensive Disks (RAID) level that provides fault tolerance, data can be irretrievably lost or become inaccessible. However, such methods require additional hardware (physically different storage device) to existing systems to be enabled.
A file allocation table (FAT) file system is a simple file system technique that organizes metadata. For example, a FAT file system uses a FAT table to list file names and data blocks associated with the file names. A FAT file system also indicates what files are free, and indicates which sectors of a hard disk drive are used for a given file. If the FAT table becomes corrupted, there may be a backup table available for repairing the corrupted FAT table. Other more advanced file systems such as the UNIX fast file system allow larger files systems to be created, and also have backup procedures.
However, the backup procedures associated with such file systems can result in high performance overhead, resulting in operation slowdown due to slower storage device accesses. For example, when a file system is used to store primarily multimedia data, such as audio and video files stored by set-top-boxes or personal video recorders, the performance overhead of file system backup procedures may result in an unacceptable delay of disk access, preventing such devices from operating efficiently during video playback or preventing some features from functioning properly. Therefore, it would be desirable to provide an improved method for handling data block corruption.